Tailoring electrolytes for Sn-based anodes toward Li storage at a low temperature of -50°C

High-capacity storage in Li-ion batteries with graphite anodes remains a challenge at low temperature. By contrast, metal-based composite anode materials, including Sn metal, have shown good lithium storage capabilities at low temperature. However, the suitable low temperature electrolyte is still infancy to achieve high efficiency capacity of Sn-based anode in ultra-low temperature. Herein, a 2-methytetrahydrofuran (2Me-THF)-based low temperature electrolyte is proven to support the excellent lithium capability of Sn-based anode at ultra-low temperatures. The formulated 2Me-THF electrolyte exhibited small changes in viscosity and ionic conductivity with decreasing temperature. A SnO2-LiF-G (graphite) electrode with 1 M lithium bis(trifluoromethanesulfonyl)imide-(2Me-THF) electrolyte maintained 80% of the room temperature reversible capacity at -30°C and delivered a reversible capacity of 650 mAh g−1, even at -50°C, under a current density of 100 mA g−1. Furthermore, a detailed characterization based on Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy and Time-of-flight Secondary ion Mass Spectrometry confirmed that the formed inorganic-rich solid electrolyte interphase on the electrode surface effectively maintained the solid-liquid interfacial stability at low temperature. This work provided design concepts for ultralow temperature electrolytes for metal-based anodes, which were especially helpful for further promoting batteries for low temperature applications.